import html2canvas from 'html2canvas'
import jspdf from 'jspdf'

const htmlToPdf = {
  getPdf(title,domId) {
    domId = '#' + domId
    html2canvas(document.querySelector(domId), {
      allowTaint: false,
      taintTest: false,
      logging: false,
      useCORS: true,
      dpi: window.devicePixelRatio*4, //将分辨率提高到特定的DPI 提高四倍
      scale:4 //按比例增加分辨率
    }).then(canvas=>{
      const pdf = new jspdf('p', 'mm', 'a4');    //A4纸，纵向
      const ctx = canvas.getContext('2d'),
        a4w = 190, a4h = 277,    //A4大小，210mm x 297mm，四边各保留10mm的边距，显示区域190x277
        imgHeight = Math.floor(a4h * canvas.width / a4w);    //按A4显示比例换算一页图像的像素高度
      let renderedHeight = 0;

      while(renderedHeight < canvas.height) {
        const page = document.createElement("canvas");
        page.width = canvas.width;
        page.height = Math.min(imgHeight, canvas.height - renderedHeight);//可能内容不足一页

        //用getImageData剪裁指定区域，并画到前面创建的canvas对象中
        page.getContext('2d').putImageData(ctx.getImageData(0, renderedHeight, canvas.width, Math.min(imgHeight, canvas.height - renderedHeight)), 0, 0);
        pdf.addImage(page.toDataURL('image/jpeg', 1.0), 'JPEG', 10, 10, a4w, Math.min(a4h, a4w * page.height / page.width));    //添加图像到页面，保留10mm边距

        renderedHeight += imgHeight;
        if(renderedHeight < canvas.height) {
          pdf.addPage();//如果后面还有内容，添加一个空页
        }
        // delete page;
      }
      //保存文件
      pdf.save(title + '.pdf')
    })
  }
}

export default {htmlToPdf}
